CHEMISTRY COMMUNITY

Akemi Karamitsos 1E

Make sure you understand reaction orders! Then definitely know which orders correspond to which integrated rate laws (and graphs) and half life equations.

Akemi Karamitsos 1E

As stated above, intermediates are produced and then consumed in multi-step reactions. Therefore, they can be canceled out when writing the overall reaction. Also, make sure that you can distinguish intermediates from catalysts. While they both cancel out in the overall reaction, catalysts are the r...

Akemi Karamitsos 1E

Does anyone know if the majority of questions will be focused on electrochemistry and kinetics since we haven't been tested on them yet?

Akemi Karamitsos 1E

In lecture today, I believe Lavelle said that the slow step is what determines the overall reaction rate/rate of formation. Also, if the early step is fast, and the later step is slow, then there is a bottleneck where a buildup of intermediate results in the first step being at about equilibrium, so...

Akemi Karamitsos 1E

Does it ever make sense to include intermediates in a rate law? Would you include them for the rate laws of elementary steps?

Akemi Karamitsos 1E

Finding the overall order of the reaction is simple once you determine the individual orders! You can simply sum up the individual orders. For example, if you have a 1st order and 2nd order reaction, the overall would be 3 because 1+2=3.

Akemi Karamitsos 1E

Also, the instantaneous rate is the change at the particular moment or the gradient at that point, while the average rate is the rate over a range of time.

Akemi Karamitsos 1E

Will these always be the units for 0, 1st, 2nd reaction rates? Or is there any circumstance where they could change?

Akemi Karamitsos 1E

After identifying the half reaction and balancing all elements, you can identify the total oxidation charge on both sides of each half reaction. Add the appropriate number of electrons to the side that has a more positive charge so that both sides become equal. Do this for both half reactions. Then ...

Akemi Karamitsos 1E

The table that we have been using for homework problems gives reduction potentials. So, the element with the highest potential is most likely to be reduced, also making it the best oxidizing agent.

Akemi Karamitsos 1E

You need to convert from acidic solution (H+) to basic solution (OH-) by adding enough OH- ions to both sides so that all H+ ions can combine with them to form water, which you will now have on both sides. Cancel the appropriate number so it only appears on one side.

Akemi Karamitsos 1E

Quick question: does it matter what species comes first in writing the cell diagrams? I know that the cathode will be on the right of the double line and the anode reaction will be on the left of the double lines, but does it matter where we put each species? For instance: Are these essentially the...

Akemi Karamitsos 1E

Does the salt bridge have anything to do with changing the mass of the electrodes of a voltaic cell? Or is change in mass only a result of the change from a solid to aqueous solution?

Akemi Karamitsos 1E

I have another question to follow up on oxidizing and reducing agents. When determining these agents, do we use the single element or the entire compound that this element is a part of? Hopefully that makes sense??

Akemi Karamitsos 1E

There are ordered rules that we use in order to assign an oxidation state to each element. Because the third rule states that "in their compounds, group-1 metals have an oxidation state of +1..." we would start by assigning K an oxidation state of +1. Rule 6 then states that oxygen atoms n...

Akemi Karamitsos 1E

Funmi Baruwa wrote:so cells represent the reaction?

In a way, yes, since the cell is made up of the two electrodes, with the cathode representing reduction and the anode representing oxidation. Together, these half-cells carry out a redox reaction for the entire cell.

Akemi Karamitsos 1E

Alex Benson wrote:Ecell is the cell potential, whereas Eocell is at the standard conditions.

To add on, these standard conditions are 1M solution or 1 atm at 25 degrees Celsius (298 K).

Akemi Karamitsos 1E

All Lavelle mentioned in lecture regarding spontaneous reduction was that if your standard reduction potential value is positive, the reaction is spontaneous.

Akemi Karamitsos 1E

In a galvanic cell, the anode side is oxidized because electrons flow towards the cathode, which is the reduced side.

Akemi Karamitsos 1E

The salt bridge connects oxidation and reduction half-cells to maintain neutrality within the circuit. This neutrality is important for the reactions to carry out.

Akemi Karamitsos 1E

In terms of Lavelle's exams, do we think the most important thing to know about entropy is a simple definition and how it relates to phase changes (solid, liquid, gas)?

Akemi Karamitsos 1E

The Van't Hoff Equation can be used to calculate K at different temperatures if delta H is known.

Akemi Karamitsos 1E

Is it always true that if delta G is negative, the reaction is spontaneous? If so, please explain!

Akemi Karamitsos 1E

Would it be a bad idea to take 14C and BL at the same time? Chem is definitely not my strongest subject. Any suggestions??

Akemi Karamitsos 1E

Unfortunately, I didn't do very well on midterm 1, so the pressure is on for midterm 2. I mostly studied using the textbook homework problems and sapling. Does anyone who did well have a strategy or study method that worked best for them? Thanks!

Akemi Karamitsos 1E

I don't believe Lavelle ever mentioned applying pressure when talking about closed systems. I think that all we need to know is that in a closed system, there is no matter exchanged with the surroundings, only energy.

Akemi Karamitsos 1E

Heat is a transfer of energy due to a temperature difference. Enthalpy is the change in amount of heat in a system at constant pressure. You can only use heat and enthalpy interchangeably if there is no work being done to the system

Akemi Karamitsos 1E

Open system: exchange of matter and energy (heat) with surroundings
Closed: no matter exchanged, only energy exchanged with surroundings
Isolated: no exchange of matter or energy with surroundings

I know these are definitions not examples, but it helps a lot with identifying systems!

Akemi Karamitsos 1E

If we have an initial volume of zero, would using the formula, w=nRT*ln(V2/V1) ever work?

Akemi Karamitsos 1E

Our constants and formulas sheet gives Cp=(5/2)R and Cv=(3/2)R. However for this question, the Cp=(7/2)R and Cv=(5/2)R. Does this mean the two are always related by subtracting 1R from Cp?

Akemi Karamitsos 1E

Im pretty sure that Lavelle only included the infinite sum relation with work/pressure/delta volume to set up his explanation of the derivation of the integral equation. Since the integral is basically the sum with infinitely small segments, I don't quite see a situation where it would be better to...

Akemi Karamitsos 1E

Is there any way to change the energy of an isolated system?

Akemi Karamitsos 1E

In a perfect system, qsys+qsur=0 since qsys=-qsur. This means that the heat gained by the system is lost by the surroundings, or vice versa, explaining the opposite signs. The phenomena is explained by the First Law of Thermodynamics, which states that heat is neither lost nor destroyed, only transf...

Akemi Karamitsos 1E

I understand that specific heat is more useful than heat capacity because it is an intensive property, but does this mean that we will probably never be using heat capacity in this class?

Akemi Karamitsos 1E

Does this mean that the salt and the water are both neutral solutions (pH=7)?

Akemi Karamitsos 1E

In what kind of problem would we need use this distinction in order to solve?

Akemi Karamitsos 1E

Breaking a bond requires energy, so this reaction is endothermic. Forming a bond releases energy, so it is exothermic.

Akemi Karamitsos 1E

Do different calorimeters each have their own specific heat capacities?

Akemi Karamitsos 1E

So to clarify, heat is not synonymous with temperature in this case? Heat is increasing but temperature is not?

Akemi Karamitsos 1E

Delta H represents the change in enthalpy, which is the total heat content of a system. So yes, the positive or negative sign of delta H should be used to determine whether a reaction is endothermic or exothermic. When it is less than zero, this means that heat has been released from the system, ind...

Akemi Karamitsos 1E

How would we determine if something is neutral given its conjugate? I'm pretty sure it has something to do with salts, but I'm still confused.

Akemi Karamitsos 1E

In the Week 2 sapling assignment, #5 asks us to find the % protonation. I got it wrong at first because I just used the initial concentration of B as the denominator, but the solution tells us to use the formal concentration, which is the sum of the concentrations of B and BH+. Can anyone explain wh...

Akemi Karamitsos 1E

If we determine that K is less than 10^-3 or, to be safe, less than 10^-4, but get an x greater than 5%, does that mean that we had a mathematical error when calculating our K? Or are we simply unable to use approximation for that particular problem?

Akemi Karamitsos 1E

Hi, I know this is probably a pretty simple answer, but could someone reiterate how Q is different than K? I'm still a bit confused.

Akemi Karamitsos 1E

Does anyone who has taken Lavelle's class in the past recommend reading the textbook consistently? Do the types of questions in the book appear on the midterms or final? Thank you!

Akemi Karamitsos 1E

MackenziePerillo-1L wrote:Does it matter what our alias is?

They recommended using our name and discussion section :) I'm assuming that makes it easier for them to give us points?

Akemi Karamitsos 1E

Are the questions that say they are due the Sunday of Week 2 the only graded homework for this course? Is everything else provided just optional/recommended/extra practice?

Akemi Karamitsos 1E

I purchased the sapling+ 7th edition ebook a few days ago from ucla and have not received a notification for the prepaid code to access sapling. Does anybody have a solution or are in a similar situation? Thanks. Hi, I had the exact same problem, because I did not previously take 14A with Lavelle. ...

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